# Energy Engineering Questions and Answers – Calorific Value of Fuels – 1

This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Calorific Value of Fuels – 1”.

1. The amount of heat liberated by complete combustion of unit quantity of fuel is known as ________
a) Agitation
b) Combustion
c) Calorific value
d) Thermogenesis

Explanation: when fuels are burnt, heat is produced. It can also be defined as the amount of heat produced on complete burning of 1gm of fuel. SI unit of calorific value is kJ/g. The chemical reaction is typically hydrocarbon or other organic molecule reacting with oxygen to form carbon dioxide and water and release heat.

2. What is the significance of calorific value?
a) Helps in deciding which fuel is good
b) Helps in locating fuel
c) Helps in deciding ignition temperature
d) Helps in deciding fire point

Explanation: The different fuels have different calorific values, i.e. different fuels produce different amount of heat in heat on burning. The calorific value of fuel helps us to decide that which fuel is good for us. This is done by comparing the calorific values of fuels with each other. Usually, a fuel having higher calorific value is considered to be a good fuel.

3. Which gas has the highest calorific value among given option?
a) Oxygen
b) Helium
c) Hydrogen
d) Nitrogen

Explanation: Hydrogen gas has the highest calorific value of 150KJ/g among all. So, hydrogen gas is considered is considered to be an extremely good fuel. However, hydrogen gas is not used as a fuel in homes and industries. Reason is hydrogen is highly combustible and it burns with explosion when lighted, its transportation from place to place is very difficult, and the cost of production of hydrogen is very high.

4. How much percent of hydrogen gas does methane contain?
a) 25%
b) 50%
c) 68%
d) 85%

Explanation: Methane contains 25% of hydrogen. Since the calorific value of fuels depends on the percentage of hydrogen present in them. So the fuels which have higher percentage of hydrogen will have higher calorific value as compared to those fuels which have lower percentage of hydrogen.

5. Which calorimeter is used to find calorific values of solid and liquid fuels?
a) Boy’s calorimeter
b) Bomb calorimeter
c) Junker’s calorimeter
d) Calvet-type calorimeter

Explanation: The calorific value of solid of solid and liquid fuel is defined as the amount of heat liberated by complete combustion of unit mass of fuel. In SI unit s it is expressed in kJ/kg. A bomb calorimeter is a type of constant volume calorimeter used in measuring heat of combustion of particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured.

6. Which calorimeter is used to find calorific values of gaseous fuels?
a) Bomb calorimeter
b) Junker calorimeter
d) Isothermal titration calorimeter

Explanation: The calorific values of gaseous fuel are defined as the amount of heat liberated by complete combustion of unit volume of fuel. SI unit is KJ/m3. This calorimeter works on principle of burning of a known volume of gas an imparting the heat with maximum efficiency to steadily flowing water and finding out the rise in temperature of a measured volume of water.

7. The calorific value of all organic compounds has the sign corresponding to a ________
a) Exothermic reaction
b) Endothermic reaction
c) Single displacement reaction
d) Synthesis reaction

Explanation: The calorific value of all organic compounds has the sign corresponding to an exothermic reaction. Because the double bond in molecular oxygen is much weaker than other double bonds or pairs of single bonds, particularly those in combustion products carbon dioxide and water, conversion of the weak bonds in o2 to the stronger bonds in CO2 and H2O releases energy as heat.

8. What value of a substance, usually a fuel or food is the amount of heat released during the combustion?
a) Energy value
b) Flash point value
c) Fire point value
d) Auto ignition

Explanation: Energy value (heating value or calorific value) of a substance, usually a fuel or food is the amount of heat released during the combustion of a specified amount of it. The energy value is characteristic for each substance. It is measured in units of energy per unit of the substance, usually mass, such as Kj/Kg, KJ/mol, and kcal/kg.

9. What accounts for the presence of water in the exhaust leaving as vapor?
a) Gross calorific value
b) Flash point value
c) Ignition temperature value
d) Net calorific value

Explanation: Gross heating value accounts for water in the exhaust leaving as vapor, and includes liquid water in the fuel prior to combustion. This value is important for fuels like wood and coal, which will usually contain some amount of water prior to burning.

10. What is the factor on which, difference between the two heating values of fuel depends on?
a) Physical properties
b) Reactants
c) Chemical composition
d) Products

Explanation: The difference between the two heating values depends on the chemical composition of the fuel. In the case of pure carbon or carbon monoxide, the two heating values are almost identical, the difference being the sensible heat content of carbon dioxide between 150oC to 25oC.

Sanfoundry Global Education & Learning Series – Energy Engineering.

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